OWC 16GB (4 x 4GB) PC8500 DDR3 1066MHz SO-DIMMs Memory Compatible with iMac 21.5" and 27" (October/2009) at Amazon.com
How to Upgrade Memory in a Late 2009 21.5-inch or 27-inch iMac - YouTube
CMS 4GB (1X4GB) DDR3 8500 1066MHZ NON ECC SODIMM Memory Ram Upgrade Compatible with Apple® Imac Intel Core 2 Duo 20" 2009 - A34 - Walmart.com
How-To: Boost your Mac's speed and prolong its useful life with easy RAM upgrades - 9to5Mac
8GB Kit (2 x 4GB) PC3-8500 RAM for Apple iMac Late 2009 - 21.5 Inch BTO/
2009 2010 Apple Mac mini IMAC macbook pro memory RAM 8GB 2x4GB DDR3 1066 1067
Memory Upgrades for Apple iMac 2009 - Up to 32GB
iMac 21.5" Late 2009 (10,1) - CPU Upgrade E8600 | MacRumors Forums
Memory RAM Upgrade for Apple iMac 20-inch Early 2009 4GB DDR3 SODIMM | eBay
Timetec 16GB KIT(4x4GB) Compatible for Apple DDR3 1067MHz / 1066MHz PC3-8500 CL7 Dual Rank for iMac (Late 2009 21.5-inch / 27-inch) SODIMM Memory MAC RAM Upgrade for iMac 10,1 and iMac 11,1 at Amazon.com